Peaking transformer



Feb. 21, 3950 L. D. DRUGMAND ET AL 2,493,119.

PEAKING TRANSFORMER Filed Aug. 5, 1948 3 LL16 I SECONDARY VOLTAGE )Lll/DK f PREMARY CURRENT Patented Feb. 21, 1950 UNITED STATES PATENTOFFICE PEAKIN G TRANSFORMER liester n. Drugmand, Greenfield, and EdwardM.

Hampe, Richfield, Wis., assignors to Cutler- Hammer, Inc., Milwaukee,Wis, a corporation of Delaware Application August 5, 1948, Serial No.42.568

The invention relates to improvements in transformers and particularlyso-called peaking transformers for supplying ignition voltage to gaseousdischarge tubes and the like.

remaining substantially constant for any further increase of saidmagnetomotive force.

Another object is to provide an improved transformer which, whenenergized by a sinusoidal primary current, induces a secondary voltagewhich both rises to and falls from its maximum amplitude abruptly, saidmaximum persisting only for an instant.

Another object is to provide such a transformer which is small for itscapacity and inexpensive to manufacture.

Another object is to provide for such a transformer an improved magneticcoupling between the primary and the secondary windings which initiallyhas high permeability but relatively low reluctance.

3 Claims. (Cl. 171-419) 2 with the secondary coil. The cross section ofthe shunt core is many times that of the core ll, but its reluctance dueto the reluctance of its air gap is much higher than the mutualreluctance of core ll.

When an alternating voltage is impressed on the primary coil H, a fluxis induced in the cores ill and It. when the current passes through zerothe reluctance of the main core II is low with respect to that of theshunt core It. Hence the major part of the initial flux pmes through themain core and as the rate of change of the flux is high it induces avoltage of high amplitude in the secondary coil l2. However, the rate ofchange of current in the primary coil and thus the rate of change ofinduced flux gradually de- Other objects and advantages will hereinafteris a primary coil ll adapted to be connected to a source of primarycurrent, and a, secondary coil II. A magnetic shunt core 13 built up ofmagnetic sheets is mounted on the primary coil l l. The shunt core has acentral leg it which passes through the center of the ,coil II and twoouter legs I! parallel to the center leg I4 and connected therewith atone end by a yoke l6.

Thus the shunt core has the shape of an E and forms an open magneticcircuit of relatively high reluctance for the primary coil H, whichcircuit with respect to the primary coil, is in parallel to the magneticcore Ill but is not interlinked creases, while the magnitude of the fluxincreases. This causes rapid saturation of the main core shortly. afterthe current passes through zero, with the result that the voltageinduced in coil l2 falls to a value closely approaching zero. Thus thevoltage induced in coil it takes a wave firm of high peaked amplitudeand short dura- Saturation of the main core causes an increased portionof the flux to pass through the shunt core. This increased flux limitsthe" current in the primary coil, thus limiting the energy demand andthe heating of the primary coil. Also this shunt reduces the aircoupling between the 7 primary and secondary coils and thus minimisestendency to produce a voltage of sinusoidal wave shape in the secondarycoil.

As stated the main core is preferably made of a single loop of flat'thinstrip'material. This assures low eddy current losses therein resultingin a higher peak voltage than would be obtainable otherwise. To furtherreduce the reluctance of the main core, the abutting ends of the stripare welded together. Instead of employing a single turn for the maincore, several strips of magnetic material arranged electrically V andmechanically in parallel may be employed.

What we claim asne and desire to secure by Letters Patent is:

l. A transformer comprising primary and secondary coils, a magneticcoupling for said coils afiording a magnetic circuit of highpermeability restricted in cross section for rapidsaturation, and aseparate magnetic shunt core mounted on said primary coil at rightangles to said magnetic coupling to minimize magnetic leakage and toprovide a magnetic circuit in parallel with said magnetic couplingrelative to said primary coil, the cross section of the second mentioned8 magnetic circuit being large relative to the cross section of thefirst mentioned magnetic circuit and including an air gap.

2. A transformer comprising primary and secondary coils, aamain magneticcore aflordinga magnetic coupling circuit free from air gaps for saidcoils, said core comprising a strap of high permeability and ofsubstantially uniform cross section ailording rapid saturation resultingin a voltage of high amplitude and short duration being induced in thesecondary coiL-and a separate magnetic shunt core of relatively largecross section mounted in right angle relation to said main magnetic coreto minimize magnetic leakage and affording an open magnetic circuit ofrelatively high reluctance in parallel with said magnetic couplingrelative to said primary coil.

3. A transformer including a main magnetic core comprising a loop offiat thin strip material of high permeability and of substantiallyuniform cross section affording rapid saturation, primary and secondarycoilsmounted thereon, said main core affording a magnetic coupling forsaid coils comprising a magnetic circuit tree from air gaps for inducingin said secondary coil a voltage of high amplitude and short duration.

ing an air gap.

LESTER D. DRUGMAND. EDWARD M. HAMPE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,340,131 Lord Jan. 25, 19442,395,881 Klemperer Mar. 5, 1945

